Piezoelectric film and method of manufacturing the same, ink jet head, method of forming image by the ink jet head, angular velocity sensor, method of measuring angular velocity by the angular velocity sensor, piezoelectric generating element, and method of generating electric power using the piezoelectric generating element

ABSTRACT

It is an object of the present invention to provide a lead-free piezoelectric film including a lead-free ferroelectric material and having low dielectric loss and high piezoelectric performance comparable to that of PZT, and a method of manufacturing the lead-free piezoelectric film. 
     The present invention is directed to a piezoelectric film comprising a (Na x Bi y )TiO 0.5x+1.5y+2     −   BaTiO 3  layer with a ( 110 ) orientation, where 0.30≦x≦0. 46 and 0.51≦y≦0.62.

This is a continuation of International Application No.PCT/JP2011/003362, with an international filing date of Jun. 14, 2011,which claims priority of Japanese Patent Application No. 2010-136962,filed on Jun. 16, 2010, the contents of which are hereby incorporated byreference.

TECHNICAL FIELD

The present invention relates to a piezoelectric film including apiezoelectric layer and a method of manufacturing the same. The presentinvention further relates to an ink jet head including the piezoelectricfilm and a method of forming an image by the head, to an angularvelocity sensor including the piezoelectric film and a method ofmeasuring an angular velocity by the sensor, and to a piezoelectricgenerating element including the piezoelectric film and a method ofgenerating electric power using the element.

BACKGROUND ART

Lead zirconate titanate (PZT: Pb(Zr_(x)Ti_(1−x))O₃, 0<x<1) is a typicalferroelectric material capable of storing a large amount of electriccharge, and used in capacitors and film memories. PZT haspyroelectricity and piezoelectricity based on the ferroelectricitythereof. PZT has high piezoelectric performance, and its mechanicalquality factor Qm can be controlled easily by adjusting the compositionor adding an element thereto. This allows PZT to be applied to sensors,actuators, ultrasonic motors, filter circuits, and oscillators.

PZT, however, contains a large amount of lead. In recent years, therehas been a growing concern that lead leached from waste may causeserious damage to the ecosystem and the environment. Accordingly, therehas been an international movement toward restricting the use of lead.For this reason, non-lead-containing (that is, lead-free) ferroelectricmaterials, unlike PZT, have been in demand.

One of the lead-free ferroelectric materials that are currently underdevelopment is, for example, a perovskite-type composite oxide[(Bi_(0.5)Na_(0.5))_(1−y)Ba_(y)]TiO₃ made of bismuth (Bi), sodium (Na),barium (Ba), and titanium (Ti). Patent Literature 1 and Non PatentLiterature 1 disclose that this ferroelectric material exhibits highpiezoelectric performance of about 125 pC/N in terms of a piezoelectricconstant d33, when the [(Bi_(0.5)Na_(0.5))_(1−y)Ba_(y)]TiO₃ hascomposition around the Morphotropic Phase Boundary with the content ofbarium y (=[Ba/(Bi+Na+Ba)]) is 5 to 10%. The piezoelectric performanceof the ferroelectric material is, however, lower than that of PZT.

Patent Literature 2, Non Patent Literature 2, and Non Patent Literature3 disclose that a (Bi,Na,Ba)TiO3 layer that is oriented in a specificdirection is fabricated.

The non-obviousness from Patent Literature 3 in view of PatentLiterature 4 is described later.

CITATION LIST [Patent Literature]

[Patent Literature 1]

Japanese Patent Publication No. H04-060073B

[Patent Literature 2]

Japanese Patent Application Publication No. 2007-266346

[Patent Literature 3]

Japanese Patent Application Publication No. 2001-261435

[Patent Literature 4]

U.S. Patent Application Publication No. 2005/0109263 (particularly,BNT-08 7 of Table 1 in page 15)

[Patent Literature 5]

International publication No. 2010/047049

[Patent Literature 6]

U.S. Pat. No. 7,870,787

[Patent Literature 7]

Chinese Patent Application Publication No. 101981718

[Non Patent Literature]

[Non Patent Literature 1]

T. Takenaka et al., Japanese Journal of Applied Physics, Vol. 30, No.9B, (1991), pp. 2236-2239

[Non Patent Literature 2]

H. W. Cheng et al., Applied Physics Letters, Vol. 85, (2004), pp. 2319-2321

[Non Patent Literature 3]

Z. H. Zhou et al., Applied Physics Letters, Vol. 85, (2004), pp. 804-806

SUMMARY OF INVENTION

One non-limiting and exemplary embodiment provides a lead-freepiezoelectric film including a lead-free ferroelectric material andhaving low dielectric loss and high piezoelectric performance comparableto that of PZT, and a method of manufacturing the piezoelectric film.

It is another object of the present invention to provide an ink jethead, an angular velocity sensor, and a piezoelectric generatingelement, each including the lead-free piezoelectric film. It is stillanother object of the present invention to provide a method of formingan image by this ink jet head, a method of measuring an angular velocityby this angular velocity sensor, and a method of generating electricpower using this piezoelectric generating element.

A piezoelectric film of the present invention comprises a(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO3 layer with a (110) orientation,where 0.30≦x≦0.46 and 0.51≦y≦0.62.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a cross-sectional view schematically showing an example of apiezoelectric film of the present invention.

FIG. 1B is a cross-sectional view schematically showing another exampleof the piezoelectric film of the present invention.

FIG. 1C is a cross-sectional view schematically showing still anotherexample of the piezoelectric film of the present invention.

FIG. 2 is a perspective view schematically showing an example of an inkjet head of the present invention and partially showing a cross sectionof the ink jet head.

FIG. 3 is an exploded perspective view schematically showing main partsincluding a pressure chamber member and an actuator part in the ink jethead shown in FIG. 2 and partially showing a cross section of the mainparts.

FIG. 4 is a cross-sectional view schematically showing an example of themain parts including the pressure chamber member and the actuator partin the ink jet head shown in FIG. 2.

FIG. 5 is a perspective view schematically showing an example of anangular velocity sensor of the present invention.

FIG. 6 is a cross-sectional view showing a cross section E1 of theangular velocity sensor shown in FIG. 5.

FIG. 7 is a perspective view schematically showing an example of apiezoelectric generating element of the present invention.

FIG. 8 is a cross-sectional view showing a cross section F1 of thepiezoelectric generating element shown in FIG. 7.

FIG. 9 is a diagram showing X-ray diffraction profiles of thepiezoelectric films according to the examples 1-6 and the comparativeexamples 1-6.

FIG. 10 is a diagram showing P-E hysteresis loops of the piezoelectricfilms according to the example 1 and the comparative example 1.

FIG. 11A shows the FIG. 2 disclosed in Patent Literature 6.

FIG. 11B shows the FIG. 2 disclosed in Patent Literature 6.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described. Inthe following description, the same reference numerals are used todesignate the same elements and parts, and therefore the overlappingdescription thereof can be omitted.

[Piezoelectric Film]

FIG. 1A shows one embodiment of a piezoelectric film according to thepresent invention. A piezoelectric film 1 a shown in FIG. 1A has amultilayer structure 16 a. The multilayer structure 16 a has anelectrode layer 13 with a (110) orientation and a(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 (0.30≦x≦0.46 and0.51≦y≦0.62) with a (110) orientation in this order. These layers 13 and15 are laminated in contact with each other. The(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 is a piezoelectriclayer. The (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 has smallleak current, high crystallinity, and high (110) orientation. Thisallows the piezoelectric film la to have low dielectric loss and highpiezoelectric performance comparable to that of PZT, although itcontains no lead.

Examples of the electrode layer 13 with a (110) orientation aredescribed below.

(1) a metal layer such as platinum (Pt), palladium (Pd), or gold (Au),and

(2) a conductive oxide layer such as nickel oxide (NiO), ruthenium oxide(RuO₂), iridium oxide (IrO₂), strontium ruthenate (SrRuO₃), orlanthanum-nickelate (LaNiO₃).

Two or more these layers may be also used.

Typically, the Pt electrode layer 13 can be formed by sputtering. The Ptelectrode layer 13 can be formed by film formation techniques such aspulsed laser deposition (PLD), chemical vapor deposition (CVD), sol-gelprocessing, and aerosol deposition (AD).

In the piezoelectric film manufacturing method of the present invention,sputtering is used to form the Pt electrode layer 13 having a (110)orientation.

The (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 is formed on thePt electrode layer 13 by sputtering.

The layer 15 with a (110) orientation is made of(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ (0.30≦x≦0.46 and 0.51≦y≦0.62).The (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 has a planeorientation of (110) on its surface.

The value of “0.5x+1.5y+2” which represents the oxygen amount insodium.bismuth titanate may include error. For example, when x=0.41 andy=0.53, the value of “0.5×0.41+1.5×0.53+2” is equal to 3. However, evenwhen the amount of sodium is 0.41 and the amount of bismuth is 0.53, theoxygen amount in sodium.bismuth titanate does not always correspond withthe value of “3”.

The thickness of the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15is not limited. The thickness thereof is at least 0.5 μm but not morethan 10 μm, for example. Even when the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻BaTiO₃ layer 15 is thin, the (Na_(x)Bi_(y))TiP_(0.5x+1.5y+2) ⁻ BaTiO₃layer 15 has low dielectric loss and high piezoelectric performance.

It is difficult to estimate the composition suitable for forming apiezoelectric layer having high crystallinity, high orientation, lowdielectric loss, and high performance equivalent to that of PZT based onthe similarity of the lattice constants or the composition of thepiezoelectric layer. This is because it is generally difficult to form athin film composed of a multicomponent composite oxide having highcrystallinity and high orientation, like (Bi,Na,Ba)TiO₃, due to adifference in the vapor pressure of each constituent element (except foroxygen) of the oxide. The present inventors have discovered that the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 has high crystallinityand high (110) orientation without use of a buffer layer.

The (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 has aperovskite-type crystal structure represented by the chemical formulaABO₃. The A site and B site in the perovskite structure have averagevalences of 2 and 4, respectively, depending on the placement of asingle element or a plurality of elements. The A site is Bi, Na, and Ba.The B site is Ti. The (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15may contain a trace amount of impurities. The impurities typically maybe Li and K to substitute for Na, and Sr and Ca to substitute for Ba, inthe A site. The impurity typically may be Zr to substitute for Ti in theB site. Examples of the other impurities may include Mn, Fe, Nb, and Ta.Some of these impurities can improve the crystallinity and piezoelectricperformance of the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15.

A (110)-oriented layer further may be optionally sandwiched between thePt electrode layer 13 and the (Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻BaTiO₃ layer 15. The (110)-oriented layer is, for example, a LaNiO₃layer or a SrRuO₃ layer.

Typically, (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 can beformed by a sputtering method. The (Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻BaTiO₃ layer 15 can be formed by other film formation techniques such asPLD, CVD, sol-gel processing, and AD as long as it has a (110)orientation.

FIG. 1B shows another embodiment of the piezoelectric film according tothe present invention. A piezoelectric film 1 c shown in FIG. 1B has amultilayer structure 16 c. The multilayer structure 16 c is a structurein which the multilayer structure 16 a shown in FIG. 1A further includesa conductive layer 17. The conductive layer 17 is formed on the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15. Particularly, themultilayer structure 16 c has the Pt electrode layer 13 having a (110)orientation, the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15having a (110) orientation, and the conductive layer 17 in this order.These layers are laminated in contact with each other.

In the piezoelectric film 1 c, the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻BaTiO₃ layer 15 is interposed between the Pt electrode layer 13 and theconductive layer 17. The Pt electrode layer 13 and the conductive layer17 can serve as an electrode layer for applying a voltage to the(Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻ BaTiO₃ layer 15, which is apiezoelectric layer.

The conductive layer 17 is composed of a conductive material. An exampleof the material is a metal having low electrical resistance. Thematerial may be a conductive oxide such as NiO, RuO₂, IrO₃, SrRuO₃, orLaNiO₃. The conductive layer 17 may be composed of two or more thesematerials. An adhesive layer improving an adhesion between theconductive layer 17 and the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃layer 15 may be provided therebetween. An example of the material of theadhesive layer is titanium (Ti). The material may be tantalum (Ta), iron(Fe), cobalt (Co), nickel (Ni), chrome (Cr), or a compound thereof. Theadhesive layer may be composed of two or more these materials. Theadhesive layer may be omitted depending on the adhesion between theconductive layer 17 and the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃layer 15.

The piezoelectric film 1 c shown in FIG. 1B can be manufactured byforming, the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 and theconductive layer 17 on the Pt electrode layer 13 in this order. Theconductive layer 17 can be formed by film formation techniques such assputtering, PLD, CVD, sol-gel processing, or AD.

The present method of fabricating a piezoelectric film can furthercomprise a step of forming the conductive layer 17 on the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15. Thus, thepiezoelectric film 1 c shown in FIG. 1B can be fabricated.

The piezoelectric film according to the present invention may furthercomprise a substrate 11 as shown in FIG. 1C. The Pt electrode layer 13is formed on the substrate.

In the piezoelectric film 1 e shown in FIG. 1C, the multilayer structure16 c shown in FIG. 1B is formed on the substrate 11.

The substrate 11 may be a silicon (Si) substrate or a MgO substrate. ASi substrate is preferred.

An adhesive layer improving an adhesion between the substrate 11 and themultilayer structure 16 c (more particularly, between the substrate 11and the Pt electrode layer 13) may be provided therebetween. However,the adhesive layer is required to be conductive. An example of thematerial of the adhesive layer is titanium (Ti). The material may betantalum (Ta), iron (Fe), cobalt (Co), nickel (Ni), chrome (Cr), or acompound thereof. The adhesive layer may be composed of two or morethese materials. The adhesive layer may be omitted depending on theadhesion between the substrate 11 and the multilayer structure 16 c.

The piezoelectric film 1 e shown in FIG. 1C can be fabricated by formingthe Pt electrode layer 13, the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃layer 15, and the conductive layer 17 on the substrate 11 in this order.

The present method of fabricating the piezoelectric film may comprise astep of forming the Pt electrode layer 13 on the substrate 11.

The piezoelectric films 1 a and 1 c shown in FIG. 1A and FIG. 1B may befabricated with use of a base substrate. Particularly, one of themultilayer structures 16 a and 16 c may be formed on the base substrateto remove the base substrate. Thus, the piezoelectric films 1 a and 1 cmay be fabricated. The base substrate may be removed by a known methodsuch as etching.

The piezoelectric film 1 e shown in FIG. 1C may be also fabricated withuse of a base substrate. In one specific embodiment, the base substratedoubles as the substrate 11. After the multilayer structure 16 c may beformed on the base substrate, the base substrate is removed.Subsequently, the multilayer structure 16 c may be disposed on thesubstrate 11 which is prepared separately. Thus, the piezoelectric film1 e may be fabricated.

The base substrate can be one of the following substrates: a substratemade of an oxide having a NaCl structure, such as MgO; a substrate madeof an oxide having a perovskite structure, such as SrTiO₃, LaAlO₃, andNdGaO₃; a substrate made of an oxide having a corundum structure, suchas Al₂O₃; a substrate made of an oxide having a spinel structure, suchas MgAl₂O₄; a substrate made of an oxide having a rutile structure, suchas TiO₂; and a substrate made of an oxide having a cubic crystalstructure, such as (La,Sr)(Al,Ta)O₃, and yttria-stabilized zirconia(YSZ). The base substrate can be formed by laminating an oxide layerhaving a NaCl type crystal structure on the surface of a glasssubstrate, a ceramic substrate such as an alumina substrate, or a metalsubstrate such as a stainless steel substrate. In this case, the Ptelectrode layer 13 can be formed on the surface of the oxide layer.Examples of the oxide layer include a MgO layer, a NiO layer, and acobalt oxide (CoO) layer.

As described above, the present method of fabricating the piezoelectricfilm may comprise a step of forming the Pt electrode layer 13 on thebase substrate directly or via another layer. After the base substratewhich can double as the substrate 11 is removed, a different substratemay be disposed. In this case, the different substrate may be disposedso that the different substrate is in contact with the Pt electrodelayer 13. The different substrate may be disposed so that the differentsubstrate is in contact with the (Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻BaTiO₃ layer 15. In the latter case, a piezoelectric film where the(Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻ BaTiO₃ layer 15, and the Ptelectrode layer 13 are formed on the different substrate in this orderis obtained.

In the following, an inkjet head, an angular velocity sensor and apiezoelectric generating element of the present invention using theabove mentioned piezoelectric film are explained. Please refer thePatent Literature 5 about the detail. The Patent Literature 6 and 7 areeach US patent publication and Chinese patent application publicationcorresponding to Patent Literature 5.

[Ink Jet Head]

An ink jet head of the present invention will be described below withreference to FIG. 2 to FIG. 4.

FIG. 2 shows one embodiment of the ink jet head of the presentinvention. FIG. 3 is an exploded view showing main parts including apressure chamber member and an actuator part in an ink jet head 100shown in FIG. 2.

A reference character A in FIG. 2 and FIG. 3 indicates a pressurechamber member. The pressure chamber member A includes through-holes 101that penetrate therethrough in its thickness direction (in the upwardand downward directions in these diagrams). The through-hole 101 shownin FIG. 3 is a part of the through-hole 101 in the cross section in thethickness direction of the pressure chamber member A. A referencecharacter B indicates an actuator part including piezoelectric films andvibration layers. A reference character C indicates an ink passagemember C including common liquid chambers 105 and ink passages 107. Thepressure chamber member A, the actuator part B, and the ink passagemember C are bonded to each other so that the pressure chamber member Ais sandwiched between the actuator part B and the ink passage member C.When the pressure chamber member A, the actuator part B, and the inkpassage member C are bonded to each other, each of the through-holes 101forms a pressure chamber 102 for storing ink supplied from the commonliquid chamber 105.

The actuator part B has piezoelectric films and vibration layers thatare aligned over the corresponding pressure chambers 102 respectively inplan view. In FIG. 2 and FIG. 3, a reference numeral 103 indicates anindividual electrode layer that is a part of the piezoelectric film. Asshown in FIG. 2, in the ink jet head 100, a plurality of individualelectrode layers 103, that is, piezoelectric films are arranged in azigzag pattern in plan view.

The ink passage member C has a plurality of common liquid chambers 105arranged in stripes in plan view. In FIG. 2 and FIG. 3, each of thecommon liquid chambers 105 is aligned over a plurality of pressurechambers 102 in plan view. The common liquid chambers 105 extend in theink supply direction (in the direction indicated by arrows in FIG. 2) inthe ink jet head 100. The ink passage member C has supply ports 106,each of which supplies the ink in the common liquid chamber 105 to oneof the pressure chambers 102, and ink passages 107, each of which ejectsthe ink in the corresponding pressure chamber 102 through thecorresponding nozzle hole 108. Usually, one pressure chamber 102 has onesupply port 106 and one nozzle hole 108. The nozzle holes 108 are formedin a nozzle plate D. The nozzle plate D is bonded to the ink passagemember C so that the nozzle plate D and the pressure chamber member Asandwich the ink passage member C therebetween.

In FIG. 2, a reference character E indicates an IC chip. The IC chip Eis connected electrically to the individual electrode layers 103, whichare exposed on the surface of the actuator part B, through bonding wiresBW. For simplicity of FIG. 2, only a part of the bonding wires BW areshown in FIG. 2.

FIG. 3 shows the configuration of the main parts including the pressurechamber member A and the actuator part B. FIG. 4 shows the cross sectionperpendicular to the ink supply direction (in the direction indicated bythe arrows in FIG. 2) in the pressure chamber member A and the actuatorpart B. The actuator part B includes piezoelectric films 104 (104 a to104 d) each having the piezoelectric layer 15 sandwiched between thefirst electrode (the individual electrode layer 103) and the secondelectrode (the common electrode layer 112). The individual electrodelayers 103 correspond one to one to the piezoelectric films 104 a to 104d. The common electrode layer 112 is a single layer electrode that iscommon to the piezoelectric films 104 a to 104 d.

As surrounded by the dashed-line in FIG. 4, the above-mentionedpiezoelectric films 104 are arranged in the ink jet head. Thepiezoelectric film is the piezoelectric film described in the itemtitled as “Piezoelectric film”.

Though not indicated in FIG. 4, as described in FIGS. 1B, 1D, 1E, themetal electrode layer 12 can be included.

[Image Forming Method by Ink Jet Head]

The image forming method of the present invention includes, in theabove-described ink jet head of the present invention, a step ofapplying a voltage to the piezoelectric layer through the first andsecond electrodes (that is, the individual electrode layer and thecommon electrode layer) to displace, based on the piezoelectric effect,the vibration layer in its film thickness direction so that thevolumetric capacity of the pressure chamber changes; and a step ofejecting the ink from the pressure chamber by the displacement.

The voltage to be applied to the piezoelectric layer is changed with therelative position between the ink jet head and an object like a sheet ofpaper, on which an image is to be formed, being changed, so as tocontrol the timing of ink ejection from the ink jet head and the amountof ink ejected therefrom. As a result, an image is formed on the surfaceof the object. The term “image” used in the present description includesa character. In other words, according to the present method for formingan image, a letter, a picture, or a figure is printed to a print targetsuch as a sheet of paper. With this method, a picturesque image can beprinted.

[Angular Velocity Sensor]

FIG. 5 shows examples of an angular velocity sensor of the presentinvention. FIG. 6 shows a cross section El of an angular velocity sensor21 a shown in FIG. 5. The angular velocity sensor 21 a shown in FIG. 5is a so-called tuning-fork type angular velocity sensor. This type ofangular velocity sensor can be used in a navigation apparatus for avehicle, and as a sensor for correcting image blurring due to handmovement in a digital still camera.

The angular velocity sensor 21 a shown in FIG. 5 includes a substrate200 having vibration parts 200 b and piezoelectric films 208 bonded tothe vibration parts 200 b.

The substrate 200 has a stationary part 200 a and a pair of arms(vibration parts 200 b) extending in a predetermined direction from thestationary part 200 a. The direction in which the vibration parts 200 bextend is the same as the direction in which the central axis ofrotation L of the angular velocity detected by the angular velocitysensor 21 extends. Particularly, it is the Y direction in FIG. 5. Thesubstrate 200 has a shape of a tuning fork including two arms (vibrationparts 200 b), when viewed from the thickness direction of the substrate200 (the Z direction in FIG. 5).

The material of the substrate 200 is not limited. The material is, forexample, Si, glass, ceramic, or metal. A monocrystalline Si substratecan be used as the substrate 200. The thickness of the substrate 200 isnot limited as long as the functions of the angular velocity sensor 21 acan develop. More particularly, the substrate 200 has a thickness of atleast 0.1 mm but not more than 0.8 mm. The thickness of the stationarypart 200 a can be different from that of the vibration part 200 b.

The piezoelectric film 208 is bonded to the vibration part 200 b. Thepiezoelectric film 208 is the piezoelectric film described in the itemtitled as “Piezoelectric film”. As shown in FIG. 5 and FIG. 6, thepiezoelectric film 208 comprises the first electrode 13 (202), thepiezoelectric layer 15, and the second electrode 17 (205).

The second electrode 205 has an electrode group including a driveelectrode 206 and a sense electrode 207. The drive electrode 206 appliesa driving voltage that oscillates the vibration part 200 b to thepiezoelectric layer 15. The sense electrode 207 measures a deformationof the vibration part 200 b caused by an angular velocity applied to thevibration part 200 b. That is, the vibration part 200 b usuallyoscillates in the width direction thereof (the X direction in FIG. 5).More particularly, in the angular velocity sensor shown in FIG. 5, apair of drive electrodes 206 are provided on both of the width-directionedge portions of the vibration part 200 b along the length directionthereof (the Y direction in FIG. 5). Only one drive electrode 206 may beprovided on one of the width-direction edge portions of the vibrationpart 200 b. In the angular velocity sensor shown in FIG. 5, the senseelectrode 207 is provided along the length direction of the vibrationpart 200 b and sandwiched between the pair of drive electrodes 206. Aplurality of sense electrodes 207 may be provided on the vibration part200 b. The deformation of the vibration part 200 b measured by the senseelectrode 207 usually is a deflection in the thickness direction thereof(the Z direction in FIG. 5).

In the angular velocity sensor of the present invention, one of thefirst electrode and the second electrode selected therefrom can becomposed of an electrode group including the drive electrode and thesense electrode. In the angular velocity sensor 21 a shown in FIG. 5,the second electrode 205 is composed of the electrode group. Unlike thisangular velocity sensor, the first electrode 202 can be composed of theelectrode group.

The first electrode 202, the drive electrode 206, and the senseelectrode 207 have connection terminals 202 a, 206 a, and 207 a,respectively, formed at the end portions thereof. The shape and positionof each of the connection terminals are not limited. In FIG. 5, theconnection terminals are provided on the stationary part 200 a.

In the angular velocity sensor shown in FIG. 5, the piezoelectric film208 is bonded to both the vibration part 200 b and the stationary part200 a. The bonding state of the piezoelectric film 208 is not limited aslong as the piezoelectric film 208 can oscillate the vibration part 200b and measure the deformation of the vibration part 200 b. For example,the piezoelectric film 208 may be bonded only to the vibration part 200b.

The angular velocity sensor of the present invention may have two ormore vibration part groups each consisting of a pair of vibration parts200 b. Such an angular velocity sensor can serve as a biaxial ortriaxial angular velocity sensor capable of measuring angular velocitieswith respect to a plurality central axes of rotation. The angularvelocity sensor shown in

FIG. 5 has one vibration part group consisting of a pair of vibrationparts 200 b.

[Method of Measuring Angular Velocity by Angular Velocity Sensor]

The angular velocity measuring method of the present invention uses theangular velocity sensor of the present invention, and includes the stepsof; applying a driving voltage to the piezoelectric layer to oscillatethe vibration part of the substrate; and measuring a deformation of thevibration part caused by an angular velocity applied to the oscillatingvibration part to obtain a value of the applied angular velocity. Thedriving voltage is applied between the drive electrode and one of thefirst electrode and the second electrode (the other electrode) thatserves neither as the drive electrode nor as the sense electrode, andthus the driving voltage is applied to the piezoelectric layer. Thesense electrode and the other electrode measure the deformation of theoscillating vibration part caused by the angular velocity.

Hereinafter, the angular velocity measuring method by the angularvelocity sensor 21 a shown in FIG. 5 is described. A driving voltagehaving a frequency that resonates with the natural vibration of thevibration part 200 b is applied to the piezoelectric layer 15 throughthe first electrode 202 and the drive electrode 206 so as to oscillatethe vibration part 200 b. The driving voltage can be applied, forexample, by grounding the first electrode 202 and changing the potentialof the driving electrode 206 (in other words, the driving voltage is thepotential difference between the first electrode 202 and the drivingelectrode 206). The angular velocity sensor 21 a includes a pair ofvibration parts 200 b that are arranged in the form of the tuning fork.Usually, reverse (positive and negative) voltages are applied to thedrive electrodes 206 provided on the respective vibration parts 200 b ofthe pair. This allows the respective vibration parts 200 b to oscillatein the mode in which they vibrate in the directions opposite to eachother (the mode in which they vibrate symmetrically with respect to thecentral axis of rotation L shown in FIG. 5). In the angular velocitysensors 21 a shown in FIG. 5, the vibration parts 200 b oscillate intheir width direction (the X direction). The angular velocity can bemeasured by oscillating only one of the pair of vibration parts 200 b.For accurate measurement, however, it is preferable to oscillate both ofthe vibration parts 200 b in the mode in which they vibrate in thedirections opposite to each other.

When an angular velocity co with respect to the central axis of rotationL is applied to the angular velocity sensor 21 a in which the vibrationparts 200 b are oscillating, the vibration parts 200 b are deflectedrespectively in their thickness direction (the Z direction) by Coriolisforce. In the case where the respective vibration parts 200 b areoscillating in the mode in which they vibrate in the directions oppositeto each other, they are deflected in the opposite directions by the samedegree. The piezoelectric layer 15 bonded to the vibration part 200 b isalso deflected according to this deflection of the vibration part 200 b.As a result, a potential difference is generated between the firstelectrode 202 and the sense electrode 207 in accordance with thedeflection of the piezoelectric layer 15, that is, the magnitude of thegenerated Coriolis force. The angular velocity co applied to the angularvelocity sensor 21 a can be measured by measuring the magnitude of thepotential difference.

The following relationship between a Coriolis force Fc and an angularvelocity ω is true:

Fc=2mvω

where v is the velocity of the oscillating vibration part 200 b in theoscillation direction, and m is the mass of the vibration part 200 b. Asshown in this equation, the angular velocity co can be calculated fromthe Coriolis force Fc.

[Piezoelectric Generating Element]

FIG. 7 shows an example of the piezoelectric generating element of thepresent invention. FIG. 8 shows a cross section F1 of a piezoelectricgenerating element 22 a shown in FIG. 7. The piezoelectric generatingelements 22 a are elements that convert externally-applied mechanicalvibration into electrical energy. The piezoelectric generating elements22 a are applied suitably to a self-sustained power supply forgenerating electric power from various vibrations including enginevibrations and driving vibrations generated in vehicles and machines,and vibrations generated during walking.

The piezoelectric generating element 22 a shown in FIG. 7 includes asubstrate 300 having a vibration part 300 b and a piezoelectric film 308bonded to the vibration part 300 b.

The substrate 300 has a stationary part 300 a, and a vibration part 300b having a beam extending in a predetermined direction from thestationary part 300 a. The material of the stationary part 300 a can bethe same as the material of the vibration part 300 b. These materialsmay, however, be different from each other. The stationary part 300 aand the vibration part 300 b made of materials different from each othermay be bonded to each other.

The material of the substrate 300 is not limited. The material is, forexample, Si, glass, ceramic, or metal. A monocrystalline Si substratecan be used as the substrate 300. The substrate 300 has a thickness of,for example, at least 0.1 mm but not more than 0.8 mm. The stationarypart 300 a may have a thickness different from that of the vibrationpart 300 b. The thickness of the vibration part 300 b can be adjustedfor efficient power generation by changing the resonance frequency ofthe vibration part 300 b.

A weight load 306 is bonded to the vibration part 300 b. The weight load306 adjusts the resonance frequency of the vibration part 300 b. Theweight load 306 is, for example, a vapor-deposited thin film of Ni. Thematerial, shape, and mass of the weight load 306, as well as theposition to which the weight load 306 is bonded can be adjustedaccording to a desired resonance frequency of the vibration part 300 b.The weight load 306 may be omitted. The weight load 306 is not necessarywhen the resonance frequency of the vibration part 300 b is notadjusted.

The piezoelectric film 308 is bonded to the vibration part 300 b. Thepiezoelectric film 308 is the piezoelectric film described in the itemtitled as “Piezoelectric film”. As shown in FIG. 7 and FIG. 8, thepiezoelectric film 308 comprises the first electrode 13 (302), thepiezoelectric layer 15, the second electrode 17 (305).

In the piezoelectric generating elements shown in FIG. 7, a part of thefirst electrode 302 is exposed. This part can serve as a connectionterminal 302 a.

In the piezoelectric generating element shown in FIG. 7, thepiezoelectric film 308 can be bonded to both of the vibration part 300 band the stationary part 300 a. The piezoelectric film 308 can be bondedonly to the vibration part 300 b.

When the piezoelectric generating element of the present invention has aplurality of vibration parts 300 b, an increased amount of electricpower can be generated. Such a piezoelectric generating element can beapplied to mechanical vibrations containing a wide range of frequencycomponents if the plurality of vibration parts 300 b have differentresonance frequencies.

[Method of Generating Electric Power Using Piezoelectric GeneratingElement]

The above-described piezoelectric generating element of the presentinvention is vibrated to obtain electric power through the firstelectrode and the second electrode.

When mechanical vibration is applied externally to the piezoelectricgenerating element 22 a, the vibration part 300 b starts vibrating toproduce vertical deflection with respect to the stationary part 300 a.The piezoelectric effect produced by this vibration generates anelectromotive force across the piezoelectric layer 15. As a result, apotential difference is generated between the first electrode 302 andthe second electrode 305 that sandwich the piezoelectric layer 15therebetween. The higher piezoelectric performance of the piezoelectriclayer 15 generates a larger potential difference between the first andsecond electrodes. Particularly in the case where the resonancefrequency of the vibration part 300 b is close to the frequency ofmechanical vibration to be applied externally to the element, theamplitude of the vibration part 300 b increases and thus the electricpower generation characteristics are improved. Therefore, the weightload 306 is preferably used to adjust the resonance frequency of thevibration part 300 b to be close to the frequency of mechanicalvibration applied externally to the element.

EXAMPLES

Hereinafter, the present invention is described in more detail withreference to examples. The present invention is not limited to thefollowing examples.

Example 1

In the example 1, a piezoelectric film having a structure shown in FIG.1C was fabricated. The piezoelectric film comprises the substrate 11,the Pt electrode layer 13, the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃layer 15 (x=0.37 and y=0.58), and the conductive layer 17 in this order.The fabrication procedure is as follows.

A Pt layer (with a thickness of 250 nm) having a (110) orientation wasformed by RF magnetron sputtering on the surface, having a planeorientation of (110), of an MgO monocrystalline substrate. The Pt layercorresponds to the Pt electrode layer 13. The Pt layer was formed usinga metallic Pt target in an argon (Ar) gas atmosphere under the filmformation conditions of an RF power of 15 W and a substrate temperatureof 300 degrees Celsius.

Next, a (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 (x=0.37 andy=0.58) (with a thickness of 2.7 μm) with a composition around theMorphotropic Phase Boundary was formed by RF magnetron sputtering on thesurface of the Pt electrode layer 13. This layer is a piezoelectriclayer. This layer 15 was formed using a target having theabove-mentioned composition in a mixed gas atmosphere of Ar and oxygen(with a flow ratio between Ar and O₂ of 50:50) under the film formationconditions of an RF power of 170 W and a substrate temperature of 650degrees Celsius.

The composition of the formed (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃layer 15 (x=0.37 and y=0.58) was analyzed by energy dispersive X-rayspectrometry (SEM-EDX). In the measurement with use of the SEM-EDX, itwas difficult to quantify a light element such as oxygen accurately,since the analysis accuracy of the light element was low. However, itwas confirmed that the composition of Na, Bi, Ba, and Ti contained inthe formed (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 (x=0.37 andy=0.58) was identical to the composition of the target.

The formed (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 (x=0.37 andy=0.58) was subjected to an X-ray diffraction analysis to analyze thecrystal structure thereof. The X-ray diffraction analysis was carriedout in such a manner that an X-ray beam was made incident from over the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15.

FIG. 9 shows the result. In the following examples and comparativeexamples, the identical X-ray diffraction analysis was used.

FIG. 9 shows the results of the X-ray diffraction profile. Observed wasonly the reflection peak derived from the (110)-oriented(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15, except for thereflection peaks derived from the MgO substrate and the Pt layer. Theintensity of the (110) reflection peak was 1,089,242 cps, which was avery high level. The profile shown in FIG. 9 means that the obtained(Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻ BaTiO₃ layer 15 has significantlyhigh (110) orientation.

Subsequently, the half value width of the (110) reflection peak derivedfrom the (Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻ BaTiO₃ layer 15 in theprofile was obtained by rocking curve measurement. The rocking curvemeasurement is a measurement in which the incident angle of the X-raybeam to the sample is scanned while the diffraction angle 2θ is fixed tothe diffraction angle of the reflection peak to be measured. The smallerthe half value width is, the higher the crystallinity is. As a result,the obtained half value width was a very small value of 0.23°. Thismeans that the (Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻ BaTiO₃ layer 15fabricated in the example 1 has extremely high crystallinity. In thefollowing examples and the comparative examples below, the same methodwas used to measure the half value widths of the reflection peaks.

Next, an Au layer with a thickness of 100 nm was formed by vapordeposition on the surface of the (Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻BaTiO₃ layer 15. This Au layer corresponds to the conductive layer 17.Thus, the piezoelectric film according to the example was prepared.

The ferroelectric property and piezoelectric performance of thepiezoelectric film were evaluated. FIG. 10 shows a P-E hysteresis loopof the piezoelectric film according to the example 1.

As shown in FIG. 10, it was confirmed that the piezoelectric filmexhibited better ferroelectric properties with an increase in thevoltage applied to the piezoelectric layer through the Pt layer and theAu layer. An impedance analyzer was used to measure the dielectric loss(tan 6) at 1 kHz. As a result, the value of tan 6 of the piezoelectricfilm was 4.6%. This means that the leak current of the piezoelectricfilm is small.

The piezoelectric performance of the piezoelectric film was evaluated inthe following manner. The piezoelectric film was cut into a strip with awidth of 2 mm and worked into a cantilever shape. A potential differencewas applied between the Pt layer and the Au layer, and the resultingdisplacement of the cantilever was measured with a laser displacementmeter. The measured displacement was converted into a piezoelectricconstant d31 to evaluate the piezoelectric performance. Thepiezoelectric constant d31 of the piezoelectric film according to theexample 1 was −163 pC/N.

Example 2

An identical experiment to that of the example 1 was performed exceptfor x=0.30 and y=0.56.

The intensity of the (110) reflection peak according to the example 2was very strong value of 447, 747 cps.

Example 3

An identical experiment to that of the example 1 was performed exceptfor x=0.46 and y=0.55.

The intensity of the (110) reflection peak according to the example 3was very strong value of 520,506 cps.

Example 4

An identical experiment to that of the example 1 was performed exceptfor x=0.38 and y=0.51.

The intensity of the (110) reflection peak according to the example 4was very strong value of 338,115 cps.

Example 5

An identical experiment to that of the example 1 was performed exceptfor x=0.39 and y=0.62.

The intensity of the (110) reflection peak according to the example 5was very strong value of 473,671 cps.

Example 6

An identical experiment to that of the example 1 was performed exceptthat manganese with a concentration of 0.2 mol % was added as anadditive to the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer (x=0.36and y=0.58).

The intensity of the (110) reflection peak according to the example 6was very strong value of 587,665 cps. The piezoelectric constant d31 ofthe piezoelectric film according to the example 6 was −221 pC/N.

Comparative Example 1

An identical experiment to that of the example 1 was performed exceptfor x=0.5 and y=0.5.

In the comparative example 1, the reflection peak derived from the(110)-oriented (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 wasobserved. However, another reflection peak derived in the(Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻ BaTiO₃ layer 15 was also observed.The intensity of the above (110) reflection peak was 71,534 cps, whichwas much lower than the peak intensity (1,089,242 cps) in the example 1.This means that the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 inthe comparative example 1 has a lower degree of orientation than the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer 15 in the examples.

The half value width of the above (110) reflection peak was 0.62°, whichwas greater than the widths in the examples. This means that the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer in the comparativeexample 1 has a lower degree of orientation than the(Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻ BaTiO₃ layer in the examples.

Next, an Au layer with a thickness of 100 nm was formed by vapordeposition on the surface of the (Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻BaTiO₃ layer so as to obtain a piezoelectric film according to thecomparative example 1.

The ferroelectric properties and piezoelectric performance of thispiezoelectric film were evaluated with use of the Pt layer and the Aulayer included in the piezoelectric film. However, a leak current in thepiezoelectric film was very large, and the ferroelectric properties(value of the remanent polarization) by the P-E hysteresis measurementwere much lower than that of the example 1 (see FIG. 10). The value oftan 6 of the piezoelectric film was 9.8%. Since the piezoelectric filmaccording to the comparative example 1 has such a large leak current,the piezoelectric constant d31 was −68 pC/N.

Comparative Example 2

An identical experiment to that of the example 1 was performed exceptfor x=0.28 and y=0.58.

The intensity of the (110) reflection peak according to the comparativeexample 2 was very weak value of 60,219 cps.

Comparative Example 3

An identical experiment to that of the example 1 was performed exceptfor x=0.48 and y=0.59.

The intensity of the (110) reflection peak according to the comparativeexample 3 was very weak value of 32,973 cps.

Comparative Example 4

An identical experiment to that of the example 1 was performed exceptfor x=0.36 and y=0.50.

The intensity of the (110) reflection peak according to the comparativeexample 4 was very weak value of 69,290 cps.

Comparative Example 5

An identical experiment to that of the example 1 was performed exceptfor x=0.40 and y=0.65.

The intensity of the (110) reflection peak according to the comparativeexample 5 was very weak value of 50,052 cps.

Comparative example 6

An identical experiment to that of the example 1 was performed exceptfor x=0.29 and y=0.43.

The intensity of the (110) reflection peak according to the comparativeexample 6 was very weak value of 32,084 cps.

The following Table 1 summarizes the results of the examples 1-6 and thecomparative examples 1-6.

TABLE 1 crystal orientation of the piezoelectric layer piezoelectriclayer orientation (110) base substrate Electrode Na(x) Bi(y) additivedirection peak intensity Effect Comparative MgO(110) Pt(110) 0.5 0.5 —plural peeks 71,534 cps Poor Example 1 including (110) ComparativeMgO(110) Pt(110) 0.28 0.58 — (110) 60,219 cps Poor Example 2 Example 2MgO(110) Pt(110) 0.30 0.56 — (110) 447,747 cps Good Example 1 MgO(110)Pt(110) 0.37 0.58 — (110) 1,089,242 cps Excellent Example 3 MgO(110)Pt(110) 0.46 0.55 — (110) 520,506 cps Good Comparative MgO(110) Pt(110)0.48 0.59 — (110) 32,973 cps Poor Example 3 Comparative MgO(110) Pt(110)0.36 0.50 — (110) 69,290 cps Poor Example 4 Example 4 MgO(110) Pt(110)0.38 0.51 — (110) 338,115 cps Good Example 1 MgO(110) Pt(110) 0.37 0.58— (110) 1,089,242 cps Excellent Example 5 MgO(110) Pt(110) 0.39 0.62 —(110) 473,671 cps Good Comparative MgO(110) Pt(110) 0.40 0.65 — (110)50,052 cps Poor Example 5 Comparative MgO(110) Pt(110) 0.29 0.43 — (110)32,084 cps Poor Example 6 Example 6 MgO(110) Pt(110) 0.36 0.58 Mn (110)587,665 cps Good

As shown in Table 1, the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer(0.30≦x≦0.46 and 0.51≦y≦0.62) 15 with a (110) orientation has high (110)orientation and high crystallinity.

In other words, the examples 1-6 to the comparative examples 1-6 revealsthat the (Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻ BaTiO₃ layer (0.30≦x≦0.46and 0.51≦y≦0.62) 15 has high (110) orientation and high crystallinity.

The example 3 and the comparative example 3 mean that x must not be over0.46.

The example 2 and the comparative example 2 mean that x must not be lessthan 0.30.

The example 5 and the comparative example 5 mean that y must not be over0.62.

The example 4 and the comparative example 4 mean that y must not be lessthan 0.51.

The example 6 means that the addition of manganese improves thepiezoelectric constant of the (Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻BaTiO₃ layer.

The addition of manganese also improves the dielectric loss of the(Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻ BaTiO₃ layer.

The invention may be embodied in other forms without departing from thespirit or essential characteristics thereof. The embodiments disclosedin this specification are to be considered in all respects asillustrative and not limiting. The scope of the invention is indicatedby the appended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

(Non-obviousness from Patent Literature 3 in view of Patent Literature4)

Patent Literature 4 discloses a piezoelectric element (see the paragraph[0004]). The BNT_(—)08 7 crystal in Table 1 of Patent Literature 4 (page15) is made of Na_(29.94)Bi_(45.79)Ti_(109.66)O_(308.78)Ba_(5.82).

Patent Literature 3 discloses piezoelectric ceramics where high (100)surface orientation is obtained stably. Particularly, Patent Literature3 discloses x(Bi_(0.5)Na_(0.5)TiO₃)−(1−x)ABO (x is not less than 0.1 andnot more than 1) which contains an excess amount of Bi by 0.1%, which ismore than the amount of Bi in the stoichiometirc proportion. An exampleof the ABO is BaTiO₃(see the paragraph [0020]).

In order to obtain high (100) surface orientation disclosed in PatentLiterature 3, the amount of Bi contained in the BNT_(—)08 7 crystal,which is disclosed in Patent Literature 4, may be increased in such amanner that the amount of Bi is over 45.79.

FIG. 11A shows an X-ray diffraction pattern of a BNT crystal which doesnot contain excess Bi (see the FIG. 2 in Patent Literature 3). FIG. 11Bshows an X-ray diffraction pattern of a BNT crystal containing excess Biby 2% (see the FIG. 2 in Patent Literature 3).

As is clear from FIG. 11A and FIG. 11B, the excess Bi lowers the (110)peak and the (111) peak. This means that the excess Bi disturbs the(110) orientation and the (111) orientation.

Accordingly, in order to increase the degree of the (110) orientation,Bi would not be added to the BNT crystal.

Specifically, since the FIG. 2 (FIG. 11A and FIG. 11B of the presentapplication) in Patent Literature 3 discloses that the excess Bidisturbs the (110) orientation and the (111) orientation, Bi is never beadded to the BNT crystal in order to enhance the degree of the (110)orientation of the BNT crystal disclosed in Patent Literature 4.

INDUSTRIAL APPLICABILITY

The piezoelectric film has a high ferroelectric property (for example,small dielectric loss) and a high piezoelectric performance, since the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer (0.30≦x≦0.46 and0.51≦y≦0.62) has high crystallinity, high (110) orientation, and smallleak current. The piezoelectric film according to the present inventionis useful as a piezoelectric film alternative to existinglead-containing oxide ferroelectrics. The piezoelectric film of thepresent invention can be used suitably for applications such aspyroelectric sensors and piezoelectric devices in which piezoelectricfilms are used. Examples of such applications are the ink jet head,angular velocity sensor and piezoelectric generating element of thepresent invention.

The ink jet head of the present invention has excellent ink ejectioncharacteristics although it does not contain a lead-containingferroelectric material such as PZT. The method of forming an image bythis ink jet head has high image forming accuracy and high expressivity.The angular velocity sensor of the present invention has highsensitivity although it does not contain a lead-containing ferroelectricmaterial such as PZT. The method of measuring an angular velocity bythis angular velocity sensor has excellent measurement sensitivity. Thepiezoelectric generating element of the present invention has excellentelectric power generation characteristics although it does not contain alead-containing ferroelectric material such as PZT. The electric powergeneration method of the present invention using this piezoelectricgenerating element has high electric power generation efficiency. Theink jet head, angular velocity sensor and piezoelectric generatingelement, and the image forming method, angular velocity measurementmethod and electric power generation method according to the presentinvention can be widely applied to various fields and uses.

REFERENCE MARKS IN THE DRAWINGS

-   11 substrate-   13 electrode layer-   15 (Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻ BaTiO₃ layer-   17 conductive layer-   16 a, 16 c multilayer structure-   101 through-holes-   102 pressure chambers-   102 a walls-   102 b walls-   103 individual electrode layer-   104 piezoelectric film-   105 common liquid chambers-   106 supply port-   107 ink passage-   108 nozzle hole-   111 vibration layer-   112 common electrode layer-   113 intermediate layer-   114 adhesive layer-   120 base substrate-   130 substrate-   200 substrate-   200 a stationary part-   200 b vibration part-   202 first electrode-   205 second electrode-   206 drive electrode-   206 a connection terminal-   207 sense electrode-   207 a connection terminal-   208 piezoelectric film-   300 substrate-   300 a stationary part-   300 b vibration part-   302 first electrode-   305 second electrode-   306 weight load

1. A piezoelectric film comprising a (Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2)⁻ BaTiO₃ layer with a (110) orientation only, where 0.30≦x≦0.46 and0.51≦y≦0.62, wherein the (Na_(x)Bi_(y))TiO_(0.5x+1.5) _(y+2) ⁻ BaTiO₃layer has composition around a Morphotropic Phase Boundary.
 2. Thepiezoelectric film according to claim 1, further comprising: a firstelectrode with a (110) orientation, wherein the first electrode and the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer are laminated.
 3. Thepiezoelectric film according to claim 2, wherein the first electrode ismade of metal.
 4. The piezoelectric film according to claim 3, whereinthe metal is platinum, palladium, or gold.
 5. The piezoelectric filmaccording to claim 4, wherein the metal is platinum.
 6. Thepiezoelectric film according to claim 1, wherein the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer contains manganese.
 7. Anink jet head comprising: a piezoelectric film having a piezoelectriclayer sandwiched between a first electrode and a second electrode; avibration layer bonded to the piezoelectric film; and a pressure chambermember having a pressure chamber for storing ink and bonded to a surfaceof the vibration layer opposite to a surface to which the piezoelectricfilm is bonded, wherein the vibration layer is bonded to thepiezoelectric film so that the vibration layer is displaceable in itsfilm thickness direction according to a deformation of the piezoelectricfilm produced by a piezoelectric effect, the vibration layer and thepressure chamber member are bonded to each other so that a volumetriccapacity of the pressure chamber changes according to a displacement ofthe vibration layer and so that the ink in the pressure chamber isejected according to a change in the volumetric capacity of the pressurechamber, and the piezoelectric layer is a(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer (0.30≦x≦0.46 and0.51≦y≦0.62) with a (110) orientation only and the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer has composition around aMorphotropic Phase Boundary.
 8. The ink jet head according to claim 7,wherein the first electrode has a (110) orientation, and the firstelectrode and the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer arelaminated.
 9. The ink jet head according to claim 8, wherein the firstelectrode is made of metal.
 10. The ink jet head according to claim 9,wherein the metal is platinum, palladium, or gold.
 11. The ink jet headaccording to claim 10, wherein the metal is platinum.
 12. The ink jethead according to claim 7, wherein the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻BaTiO₃ layer contains manganese.
 13. A method of forming an image by anink jet head, comprising: preparing the ink jet head, wherein the inkjet head includes: a piezoelectric film having a piezoelectric layersandwiched between a first electrode and a second electrode; a vibrationlayer bonded to the piezoelectric film; and a pressure chamber memberhaving a pressure chamber for storing ink and bonded to a surface of thevibration layer opposite to a surface to which the piezoelectric film isbonded, the vibration layer is bonded to the piezoelectric film so thatthe vibration layer is displaceable in its film thickness directionaccording to a deformation of the piezoelectric film produced by apiezoelectric effect, the vibration layer and the pressure chambermember are bonded to each other so that a volumetric capacity of thepressure chamber changes according to a displacement of the vibrationlayer and so that the ink in the pressure chamber is ejected accordingto a change in the volumetric capacity of the pressure chamber, and thepiezoelectric layer is a (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer(0.30≦x≦0.46 and 0.51≦y≦0.62) with a (110) orientation only and the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer has composition around aMorphotropic Phase Boundary; and applying a voltage to the piezoelectriclayer through the first electrode and the second electrode to displace,based on the piezoelectric effect, the vibration layer in its filmthickness direction so that the volumetric capacity of the pressurechamber changes and the ink is ejected from the pressure chamber by thedisplacement.
 14. The method according to claim 13, wherein the firstelectrode has a (110) orientation, and the first electrode and the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer are laminated.
 15. Themethod according to claim 14, wherein the first electrode is made ofmetal.
 16. The method according to claim 15, wherein the metal isplatinum, palladium, or gold.
 17. The method according to claim 16,wherein the metal is platinum.
 18. The method according to claim 13,wherein the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer containsmanganese.
 19. An angular velocity sensor comprising: a substrate havinga vibration part; and a piezoelectric film bonded to the vibration partand having a piezoelectric layer sandwiched between a first electrodeand a second electrode, wherein the piezoelectric layer is a(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer (0.30≦x≦0.46 and0.51≦y≦0.62) with a (110) orientation only and the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer has composition around aMorphotropic Phase Boundary, and one of the first electrode and thesecond electrode selected therefrom is composed of an electrode groupincluding a drive electrode for applying a driving voltage thatoscillates the vibration part to the piezoelectric layer and a senseelectrode for measuring a deformation of the vibration part caused by anangular velocity applied to the oscillating vibration part.
 20. Theangular velocity sensor according to claim 19, wherein the firstelectrode has a (110) orientation, and the first electrode and the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer are laminated.
 21. Theangular velocity sensor according to claim 20, wherein the firstelectrode is made of metal.
 22. The angular velocity sensor according toclaim 21, wherein the metal is platinum, palladium, or gold.
 23. Theangular velocity sensor according to claim 22, wherein the metal isplatinum.
 24. The angular velocity sensor according to claim 19, whereinthe (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer contains manganese.25. A method of measuring an angular velocity by an angular velocitysensor, comprising: preparing the angular velocity sensor, wherein theangular velocity sensor includes: a substrate having a vibration part;and a piezoelectric film bonded to the vibration part and having apiezoelectric layer sandwiched between a first electrode and a secondelectrode, the piezoelectric layer is a (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2)⁻ BaTiO₃ layer (0.30≦x≦0.46 and 0.51≦y≦0.62) with a (110) orientationonly and the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer hascomposition around a Morphotropic Phase Boundary, and one of the firstelectrode and the second electrode selected therefrom is composed of anelectrode group including a drive electrode and a sense electrode;applying a driving voltage to the piezoelectric layer through the driveelectrode and the other of the first electrode and the second electrodeselected therefrom to oscillate the vibration part; and measuring,through the other electrode and the sense electrode, a deformation ofthe vibration part caused by an angular velocity applied to theoscillating vibration part to obtain a value of the applied angularvelocity.
 26. The method according to claim 25, wherein the firstelectrode has a (110) orientation, and the first electrode and the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer are laminated.
 27. Themethod according to claim 26, wherein the first electrode is made ofmetal.
 28. The method according to claim 27, wherein the metal isplatinum, palladium, or gold.
 29. The method according to claim 28,wherein the metal is platinum.
 30. The method according to claim 25,wherein the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer containsmanganese.
 31. A piezoelectric generating element comprising: asubstrate having a vibration part; and a piezoelectric film bonded tothe vibration part and having a piezoelectric layer sandwiched between afirst electrode and a second electrode, wherein the piezoelectric layeris a (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer (0.30≦x≦0.46 and0.51≦y≦0.62) with a (110) orientation only and the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer has composition around aMorphotropic Phase Boundary.
 32. The piezoelectric generating elementaccording to claim 31, wherein the first electrode has a (110)orientation, wherein the first electrode and the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer are laminated.
 33. Thepiezoelectric generating element according to claim 32, wherein thefirst electrode is made of metal.
 34. The piezoelectric generatingelement according to claim 33, wherein the metal is platinum, palladium,or gold.
 35. The piezoelectric generating element according to claim 34,wherein the metal is platinum.
 36. The piezoelectric generating elementaccording to claim 31, wherein the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻BaTiO₃ layer contains manganese.
 37. A method of generating electricpower using a piezoelectric generating element, comprising: preparingthe piezoelectric generating element, wherein the piezoelectricgenerating element includes: a substrate having a vibration part; and apiezoelectric film bonded to the vibration part and having apiezoelectric layer sandwiched between a first electrode and a secondelectrode, and the piezoelectric layer is a(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer (0.30≦x≦0.46 and0.51≦y≦0.62) with a (110) orientation only and the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer has composition around aMorphotropic Phase Boundary; and vibrating the vibration part to obtainelectric power through the first electrode and the second electrode. 38.The method according to claim 37, wherein the first electrode has a(110) orientation, wherein the first electrode and the(Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer are laminated.
 39. Themethod according to claim 38, wherein the first electrode is made ofmetal.
 40. The method according to claim 39, wherein the metal isplatinum, palladium, or gold.
 41. The method according to claim 40,wherein the metal is platinum.
 42. The method according to claim 37,wherein the (Na_(x)Bi_(y))TiO_(0.5x+1.5y+2) ⁻ BaTiO₃ layer containsmanganese.